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The aim of this investigation is to provide a classification and examples of N—H …π (and also O—H …π) bonds to the aromatic π systems in organic ammonium tetraphenylborates that would serve as reference for X—H …π(arene) bonds in general. To this end the crystal structures of the tetraphenylborates of the following cations have been determined: Me3NH+, Et3NH+, quinuclidinium, DabcoH+, Et(iso-Pr)2NH+ (monohydrate), (Ph3B)NH[—(CH2)2—]2NHMe+ (Me2CO solvate), Me2NH2+ (MeCN and Et2CO solvates), Et2NH2+, (iso-Pr)2NH2+, azoniacycloheptane, guanidinium (monohydrate), MeNH3+, EtNH3+, and 1-adamantammonium (monohydrate). These structures contain a variety of normal, bifurcated, and trifurcated N—H …π bonds as well as normal O—H …π bonds to the phenyl groups of the anion. The X—H …π bonds will form whenever opportunity arises, even though the result may be unfavourable bonding geometry. Branched bonds and orientational disorder represent compromise solutions in situations where the H(X) hydrogens are presented with competing phenyl acceptors or where the general organization of the crystal structure offers unfavourable bonding conditions to these hydrogens. The distributions of the distances from X or H(X) to the centre of the phenyl-ring skeleton are analyzed in detail, as are also those of the mean X … C and H(X)… C distances to the ring carbons.

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The title compounds, C28H31N2O3(+)-Cl(-)-H2O (common name rhodamine-6g), (I), and C21H17N2O3(+)-Cl(-)-3H2O (common name rhodamine-123), (II), both have planar xanthene skeletons with a formal +1 charge on the amino N atoms delocalized through the pi-electron system so that the N-Csp(2) bond distances indicate significant double-bond character. The substituted planar phenyl groups make angles of 63.29 (8) and 87.96 (11) degrees with the xanthene planes in (I) and (II), respectively. In both molecules, the carbonyl bond vectors point toward the xanthene rings. The ethylamine groups in (I) are oriented similarly with their CH2-CH3 bond vectors pointing nearly perpendicular to the xanthene plane. The chloride ions and water molecules are disordered in both structures. In (I), the chloride ion and water molecule are disordered between two sites. One water and chloride alternately occupy the same site with occupancy factors of 0.5. The other 0.5-chloride and 0.5-water occupy two distinct positions separated by 0.747 (8) A. In (II), the chloride ion is disordered between three sites and one of the waters is disordered about two other sites. Both crystal structures are stabilized by hydrogen bonds involving the chloride ions, amino groups and water molecules, as well as by pi-pi stacking between xanthene planes.

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. Recrystallization of a primary or secondary alkylammonium tetraphenylborate (TB) from approximately 1 : 1 mixtures of Me2C0 (or MeEtCO) and water yields, against expectation, the TB of the corresponding iminium cation and thus provides an easy route to a variety of aliphatic Schiff bases. The crystal structures of five such salts have been de- are discussed in detail, as also is the tendency of the small iminium ions to orientational disorder. The range of the C=N bond length in these and other iminium salts is quite narrow, with 1.283(12) A as the mean (uncorrected) value. Where a hydrogen atom(s) is attached to the iminium nitrogen, it will form a hydrogen bond (simple or bifurcated) with the aromatic n system of the nearest phenyl ring(s). The narrowness of the C=N bond-length range with respect to substitution on the cation has prompted a detailed 6-31G" ab ir~itio study of the effect, on the geometry of the [H,c=NH,]+ ion, of a partial or complete replacement of the H atoms by one of the following substituents: F, C1, CN, Li, and Na. The 46 structures optimized in planar geometry were supplemented by a number of optimizations of similarly substituted ethylenes as well as by a few optimizations in perpendicular geometry. Analysis of the numerical results involves the bond lengths and angles, Mulliken EM and (in part) Lijwdin EL net charges on the atoms, and electron densities p, = p(r,) at the bond critical points. Only a limited use has been made of comparisons involving the total electronic energies E (substitutional isomerism). Since the above substituents span the entire electronegativity scale, and CN provides for the possibility of conjugation, the effects they produce are expected to bracket the effects that would be produced by any other substituents. The calculations confirm the essential narrowness of the C=N bond-length range in iminium ions. They also show that, at least in the 6-31G:!: scheme, the nitrogen in [H'C=NH,]+ carries a significant negative net charge (both in terms of EM and e,), which is contrary to the conventional representation of the ion as H2C=N+H2. The trends observed in the parameters are smooth and highly self-consistent except for the tri-and tetrasubstituted ions containing Li or Na, where interligand repulsions may invalidate the assumption of planarity. Many of the parameters can be represented to a high degree of correlation as linear functions a, + actzc(X) + aNtl,(X) of the numbers tz of substituent atoms X on the C and N atoms. This representation makes it possible to estimate the contribution to the parameter value from the substitution at the distant atom of the C=N bond, i.e., the extent of localization of the effect produced by the substituent. The success of the linearization of the parameter variation raises the important question of whether the apparent additivity is genuine and intrinsic or merely a property of the 6-31G:': optimization scheme. In other words, will additivity be retained, functionally, for sets of parameters obtained from higher level ab ini...

. 1527 (1987). 65,The crystal chemistry of complex In(II1) halides is discussed and compared with that of other Group 111 elements and Fe(III), with critical comments and analysis of the available information. The cation/anion packing types occurring among A+ [M3+X4] halides are classified according to volume per formula unit and the relative ionic sizes of M, X, and A, and the structural trends in this class of compounds are identified. The effect of systematic factors responsible for variation in M(II1)-C1 bond lengths is examined in detail. It is shown that the mean M(II1)-C1 bond lengths in [MC1,,L,,,Ie (M = Al, Ga, Fe, In, T1; L = C1 or a neutral ligand) complexes can be approximated, to within about 0.02 A, by a linear function of the coordination number CN = n + m and the charge E over the range 3 5 CN 5 6 and -3 5 E 5 2. This analytical expression provides a norm for comparing M(II1)-Cl bond lengths and demonstrates that the CN is always a more important factor than E in determining thevariation in the mean bond length and that it becomes dominant when M is small. The crystal structure of (Me2NH2) The water in K31nC16. nH20 appears to be in part zeolitic; the hydrate examined contained more water than the monohydrate reported previously. Hydrogen bonding in these and related structures is described and discussed in detail; descriptions of the hydrogen-bonding schemes in (NH4) 65, 1527 (1987).On discute de la chimie des cristaux des complexes des halogknures de l'In(II1) et on la compare a celle des complexes du Fe(II1) et des autres tlCments du groupe 111; on fait des commentaires critiques ainsi qu'une analyse des informations disponibles. In this contribution to the structural chemistry of In-halogen compounds we offer ( A ) a catalogue raisonne' of the crystal chemistry of halogeno complexes of In(II1) and related compounds; (B) a detailed analysis of the systematic factors responsible for variation in M-Cl bond lengths in Group I11 and Fe(II1) complex chlorides, and a resulting scheme which permits these bond lengths to be rationalized and predicted; (C) crystal-structure determinations or re-determinations of the four title compounds; and (D) a discussion of hydrogen bonding in these and other In(II1) halides. Our discussion of the crystal 'To whom correspondence may be addressed.older of NSERC (1983of NSERC ( -1986 and Killam (1984Killam ( -1986 chemistry attempts not merely to unify results published to date, but also to offer critical comment and identify gaps in our present knowledge. It therefore includes complex In(II1) fluorides, which are usually treated as belonging to the solidstate rather than to the coordination chemistry of indium, even though their structures often contain recognizable InF,,E units (some of which may exist in fluoride melts). A few pseudohalogeno complexes are also mentioned. On the other hand, halogeno complexes containing In-C bonds have been deliberately excluded; the presence of the covalent In-C bond introduces factors, additional to the coordination number (C...

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